1) Field of the Disclosure
The disclosure relates generally to methods and systems of fabricating sensors, and more particularly, to methods and systems for fabricating nanoparticle piezoelectric sensors deposited onto a structure.                2) Description of Related Art        
Small sensors, such as microsensors, may be used in a variety of applications including in structural health monitoring (SHM) systems and methods to continuously monitor structures, such as composite or metal structures, and to measure material characteristics and stress and strain levels in order to assess performance, possible damage, and current state of the structures. Known SHM systems and methods may include the use of small, stiff, ceramic disk sensors integrated onto a polyimide substrate and connected to power and communication wiring. Such known sensors are typically manually bonded to a structure with an adhesive. Such manual installation may increase labor and installation costs and such adhesive may degrade over time and may result in the sensor disbonding from the structure. In addition, such known sensors may be made of rigid, planar, and/or brittle materials that may limit their usage, for example, usage on a curved or non-planar substrate surface may be difficult. Moreover, in a large array of such known sensors, the amount of power and communication wiring required may increase the complexity and the weight of the structure.
In addition, known sensor systems and methods, such as micro-electromechanical systems (MEMS) and methods, may include the use of depositing onto a substrate piezoelectric sensors, such as lead zirconate titanate (PZT) sensors, having nanoparticles. Known methods for making such MEMS may include molten salt synthesis of PZT powder for direct write inks. However, the applications of the PZT sensors fabricated with such known methods may be limited by the physical geometry of the PZT sensors. Such physical geometry limitations may result in inadequate sensing capacities or inadequate actuation responses. Further, the PZT sensors fabricated with such known methods may be unable to be applied or located in areas where their function may be important due to the PZT sensor fabrication method. For example, known molten salt synthesis methods may require processing at higher temperatures than certain application substrates can tolerate.
Further, such known MEMS systems and methods may also include the use of sensors having nanoparticles which have not been crystallized and which may be less efficient than nanoparticles which have been crystallized. Non-crystallized structures typically have greater disorganization resulting in decreased response sensitivity to strain and voltage, whereas crystallized structures typically have greater internal organization resulting in increased response sensitivity to strain and decreased necessity for energy to operate. In addition, the nanoparticles of the sensors may be too large for some known deposition processes and systems, such as a jetted atomized deposition (JAD) process, and such nanoparticles may require a high temperature sintering/crystallization process which may result in damage to temperature sensitive substrates or structures.
Accordingly, there is a need in the art for an improved method and system of fabricating PZT piezoelectric sensors having nanoparticles that may be used in structural health monitoring systems and methods for structures, where such improved method and system provide advantages over known methods and systems.